This year, 6 types of voters will decide the presidential election

Democratic presidential candidate Barack Obama leads Republican John McCain in the latest USA TODAY/Gallup Poll by only single digits among registered voters, 48%-42%, at the edge of the survey's margin of error.

However, an analysis of how Americans view the election — whether they think it matters and how strongly they're committed to a candidate — shows a more lopsided contest.

USA TODAY used results from a national survey of 1,625 adults to sort the electorate into six broad groups based on their level of engagement and enthusiasm about the election.

Obama dominates the two most energized groups of voters, 44% of the electorate combined, who are focused on a range of issues and say they won't change their choice of candidate between now and November. McCain's strongholds are two groups of voters at the other end of the spectrum, 28% of the electorate in all, who are skeptical that the election results will make any difference in their lives and are less enthusiastic about voting than usual.

A cluster of more upbeat GOP-leaning voters remains in the middle and up for grabs.

In all, 67% of Obama supporters say they're more excited than usual about voting, compared with 31% of McCain backers. A 54% majority of McCain voters report being less excited than usual.

Political strategists who have run national campaigns say that enthusiasm gap underscores an uphill climb ahead for McCain — and reflects a risk for Obama. Everything is harder when your backers are downbeat, says Tony Fabrizio, the pollster for Republican Bob Dole's 1996 presidential campaign, which struggled to generate voter excitement.

"It is very difficult to raise money if there's not a level of enthusiasm," he says. "It is very difficult to put people out on the street. It's very difficult to have a national organization, or to get people to rallies and events." He's seen a "stark contrast" between the ability of McCain and Obama to draw big crowds and raise money.

If there is a silver lining for McCain, it's this: At a time President Bush's approval rating is 28% and fewer Americans identify themselves with the GOP than at any time in decades, those backing the Arizona senator are likely to stick with him. What's more, they tend to be older people who reliably vote.

Obama, in contrast, has inspired enormous enthusiasm among younger voters, who in the past have been less likely to show up at the polls.

Their participation will help reshape the electoral map if they stay engaged, says Joe Trippi, a strategist for Democrat Howard Dean's youth-driven presidential bid four years ago. But "all that energy sometimes is fragile if you make a big mistake," he cautions. "When you have a bunch of people who are very enthusiastic, it's easier to disappoint them."

Even so, Trippi adds, "I'd rather have the energized people."

The USA TODAY analysis is based on four questions from the poll, taken June 15-19:

• Compared to previous elections, are you more or less enthusiastic than usual about voting?

• How much difference do you think the election result will make to you and your family?

• Do you have a favorable or unfavorable opinion of John McCain and of Barack Obama?

• Are you certain now whom you will vote for, or do you think you may change your mind?

Here's what the analysis found.

1. True believers:30% of the electorate

Nearly one-third of those surveyed could be called the true believers of this campaign.

They're excited about the election, sure of their choice and unfavorably inclined toward the other guy. They see the stakes as high: Two-thirds say the election will make a great deal of difference to them and their families, the most of any voter group. Eight of 10 feel more enthusiastic than usual about voting this year.

John McCain has some support among this group of the year's most intense voters, but Barack Obama has more. By 2-1, such voters back the Democrat.

This group includes the highest percentage of women, African Americans and liberals — the sort of voters who fueled record turnout in a string of Democratic primaries this year. They express the most concern that McCain will pursue policies similar to those of President Bush, and they give the former Navy fighter pilot the lowest rating as a potential commander in chief.

"I know who I'm going to vote for," Renee Prigmore-Onwu, an Obama supporter from Nashville, says firmly. She works as a child care provider. Her biggest issue is the struggle to make ends meet for her and her three children, ages 16, 11 and 9. "Gas prices plus the cost of food — everything's going up except wages," she says.

Prigmore-Onwu, 46, has watched the campaign closely, supporting New York Sen. Hillary Rodham Clinton during the Democratic primaries but now loyal to Obama.

"A black man running for president — this has been a long time coming," she says.

"Then of course Hillary Clinton being a woman as well — it made history."

2. Fired up & favorable:14% of the electorate

Like the "true believers," voters in the second group are overwhelmingly more enthusiastic than usual about voting. Unlike the first group, though, nearly all of them view McCain and Obama favorably.

Members of this group have been the face of Obama's primary campaign: They have the lowest average age — a third are younger than 35 — and the highest average income. More of them have a college education than any other group.

They're confident in the ability of either candidate to handle the Oval Office — the least likely to worry about whether Obama has enough experience to be president, for instance, and the most likely to rate both Obama and McCain as capable of serving as commander in chief.

That would seem to make them a swing group, but voters in this category say their minds are settled. By nearly 2-1, they support Obama.

Daniel Seagull, 33, a middle-school science teacher from South Glastonbury, Conn., admires McCain for his days as a Republican maverick.

"You knew where he stood and if you didn't like it, too bad," he says. He's solidly for Obama, though, drawn by a message during the primaries that Seagull shorthands as " 'change, change, change' and 'yes we can.' "

In recent weeks, he's been disappointed in each candidate. "It's become the same old story that you see in every election, with the candidates attacking each other and 'blah, blah, blah,' " he says, fretting Obama has become a "play-it-safe" candidate.

Even so, Seagull has a suggestion if Obama becomes president. "Idealistically, if we took one day's worth of spending on the Iraq war and put it toward a Manhattan Project for alternative energy, I would think we could get pretty far," he says.

3. Firmly decided:12% of the electorate

In a year when many Democrats are keyed up and Republicans discouraged, this group isn't the norm. Nearly eight in 10 say their level of enthusiasm about voting is "about the same as usual." A small fraction of any other group reports seeing this year's campaign as business as usual.

These voters tend to have higher incomes and be older than the average, and they include the highest percentage of registered voters. More than a third hold post-graduate degrees.

Although they are closely divided — 50% for McCain, 48% for Obama — few swing voters are in this group. Almost all of them say they have made up their minds about their vote.

Diana Sparklin's choice is McCain, though she's not convinced he'll succeed enough to win a second term, assuming he manages to win a first. "I feel safer" with the Arizona senator, she says. "I feel he's older and more experienced, and he has some war experience background."

Sparklin, 69, retired to Lady Lake in central Florida 3½ years ago after working as a specialist on foreign patent applications for a law firm in Wilmington, Del. For her, global issues such as climate change, turmoil in Africa and conflict in the Middle East are major concerns.

Obama's relative lack of experience and his association with Jeremiah Wright, whose sermons blasting the United States for racism caused controversy, give her pause. "You just don't separate on a verbal basis" from a longtime pastor, she says of Obama. "I'm afraid he has taken (Wright's views) in his mind."

4. Up for grabs:18% of the electorate

These voters are squarely in the middle. They tend to have favorable views of both candidates and are the most likely to say either would make a good president, but they aren't yet settled in their choice. They aren't paying as much attention to the campaign as the most engaged voters in the first two groups, but they're also not as disenchanted as those in the last two groups.

One in four of those in this group say they're undecided about whom to support, and the rest say they might change their mind before Election Day.

This battleground group has a GOP tilt. It includes the highest percentage of whites of any group and more of those who attend church every week. McCain needs to make major inroads with them to offset Obama's edge among other voters.

Stephanie Clemens cast her first presidential vote for Bush in 2004. This year, the 23-year-old student from Chico, Calif., sees a lot to like in both contenders. McCain "has strong leadership and he seems like an approachable person," she says. She admires Obama's idea of "a change, something different." She can't think of anything she doesn't like about either one.

She does have definite views about which issues matter most to her. She's studying at California State University-Chico and considering a career in human resources management or event planning. "College tuition, health care, the economy, gas prices," she says, ticking them off. "These are things that affect my life."

5. Skeptical & downbeat:12% of the electorate

The election's most downbeat voters are the least enthusiastic about voting and skeptical about whether the election will make a difference for them and their families. They give Bush his lowest approval rating of any group.

They aren't excited about the contenders to succeed the president, either. Four in 10 haven't decided whom to support, by far the largest of any group, and the rest are open to changing their minds.

Voters in this group are older than average and the least likely to have a college education. It includes the highest percentage of those who live in small towns and rural areas.

They favor McCain over Obama by 11 percentage points, but can he persuade more of them to support him — and then turn out to vote?

Joe Heiser, 49, a steelworker from Pittsburgh and an independent, has qualms about both candidates. McCain "might be a little bit too old" for the job, he worries. Obama "has more passion as to what he's trying to achieve," but Heiser wonders whether he'll be able to deliver on his promises. Most politicians don't, he says.

Heiser's biggest concerns are economic, "health care for the elderly and the way things are rising in costs." He's concerned about securing U.S. borders and resolving the Iraq war. His expectations that anything will change are low, however, one reason he questions whether it really matters who wins.

"I'm not too excited about it," he says. "It turns out to be the same, no matter who is in there."

6. Decided but dissatisfied:16% of the electorate

Don't tell voters in this group that elections matter: Not one of them says the campaign outcome will make much difference to them or their families. By 2-1, they are less enthusiastic than usual about voting. Still, in contrast to the previous "skeptical and downbeat" group, all of these voters say their minds are firmly made up.

They include the highest percentage of conservatives and Republicans of any group, and they give Bush his highest job-approval rating, albeit still just 37%. This group is the least likely to see the Iraq war as a mistake, although 51% say that it was.

That underscores a quandary for McCain. The groups that clearly favor the Arizona senator are the two final ones. One gives Bush his highest rating, the other his lowest. One group has the fewest members who say invading Iraq was a mistake; the other has the most. Bridging that divide and building support from both groups could be a challenge, especially when it comes to calibrating how closely to embrace Bush.

National security concerns drive the "decided but dissatisfied" voters. It is the only group in which a majority favors a candidate whose strength is protecting the country from terrorism rather than fixing the economy, and the only group in which a majority doubts Obama can handle the responsibilities of commander in chief. This group is McCain's base, the only one in which his support tops 50%.

David McLen, 53, from a town north of Houston called Spring, admires McCain's military service but worries that he's not really a conservative. Obama, though, is "to the left of me on just about everything," says McLen, who works in the oil business, verifying land and mineral claims before drilling begins.

He supports more domestic exploration of oil, is concerned about the economy and illegal immigration and calls security issues "very important," though he's come to question the war. "What are we doing there, and when will we leave?" he asks.

In the Republican primaries, McLen preferred nearly every GOP presidential contender over McCain. He voted for former Massachusetts governor Mitt Romney in the Texas primary, liked former Arkansas governor Mike Huckabee and was intrigued by some of what Texas Rep. Ron Paul had to say.

"I don't think either of these candidates are evil," McLen says of McCain and Obama, "but to use the cliché, I'm choosing the lesser of two evils."